Distribution and excretion of two phthalate esters in rats, dogs and miniature pigs

Abstract Diisooctyl phthalate (DIOP) or butylglycolylbutyl phthalate (BGBP) was administered in the diet to male Sprague-Dawley rats, beagle dogs and miniature pigs in a dose of 50mg/kg for 21-28 days before oral administration of a single dose of the same compound labelled with 14 C in the carbonyl group. The animals were killed and tissues, faeces and urine were analysed for 14 C at various times after the dose of [ 14 C]phthalate was administered. In the rat, approximately half of the 14 C activity from labelled DIOP was excreted in the urine and half in the faeces, while radioactivity from this phthalate appeared predominantly in the faeces in dogs (69-80%) and in the urine in pigs (65-86%). The BGBP label was excreted mainly in the urine in rats (77-83%), dogs (72-75%) and pigs (68-89%). Extraction of the tissues for metabolites indicated that DIOP was less readily metabolized than BGBP by all three species. The nature of the substituent on the phthalate molecule appears to influence the excretion of the phthalate-ester metabolites.